This invention relates to automated semiconductor wafer processing systems for performing liquid and gaseous processing of wafers. Such systems can be used to process semiconductor wafers, data disks, semiconductor substrates and similar articles requiring very low contaminant levels.
The processing of semiconductor wafers has become of great economic significance due to the large volume of integrated circuits, data disks, and similar articles being produced.
The size of features used in integrated circuits and data disks have decreased significantly, thus providing greater integration and greater capacity. This has been possible due to improved lithography techniques and improved processing.
The reduction in feature size has been limited by contamination. This is true because various contaminating particles, crystals, metals and organics lead to defects in the resulting products. The limitations on feature size caused by contaminants have prevented full utilization of the resolution capability of known lithography techniques.
Thus there remains an acute need for improved methods and systems for processing semiconductor wafers, data disks and similar articles requiring very low levels of contamination during processing.
During the fabrication of semiconductor components, various manufacturing steps involve the application of processing liquids and gases to the articles being processed. The application and removal of these processing fluids to and from the exposed surfaces of the wafers are enhanced by movement of the wafers within the processing chamber. Processing is also enhanced by centrifugal action of the semiconductor wafers which improves movement of fluids across the wafer surfaces, such as when liquids are sprayed upon the wafer and then move across the wafer surfaces due to centrifugal forces acting upon the liquids as the wafers spin.
As one example, after semiconductor wafers have been cleaned, they must be dried. This is not a trivial process because any water that remains on the surface of a semiconductor wafer has at least some potential of leaving some form of residue which may interfere with subsequent operations or cause defects in the resulting products. Centrifugal action aids in the removal of water and other processing liquids so that such residues are not as likely to occur because the fluid is applied to the surface and then moves outwardly and is removed from the surfaces. Drying is also benefitted because less liquid remains on the wafer surfaces, so drying speed is increased. This saves processing time and reduces the risk of residue or contamination due to particle adhesion.
In one type of prior art centrifugal processor, several wafer carriers are put in holders or carriers in a spaced substantially circular array around the axis of rotation. The rotor with loaded carriers of wafers is then rotated within a processing chamber which is typically enclosed within a processing bowl or vessel. In the center of the vessel and at other peripheral locations are fluid manifolds with spray nozzles or similar inlets that are connected to a source of deionized water, heated nitrogen, or other processing chemicals both liquids and gases. These or other processing fluids are thus applied to the wafers to effect washing, drying or other processing.
Other prior art spin rinser dryers have been built for drying batches of wafers held in a single wafer carrier. The wafer carrier and supported wafers are held within a rotor. The rotor has an opening for receiving the carrier with the wafers positioned in an array with the centerpoints of the wafers at or nearly aligned with the axis of rotation. Typically a small offset is used so that the wafers will seat into the wafer carriers as centrifugal forces are developed during rotation. The water, nitrogen or other processing fluids come into the chamber along the sides rather than through a manifold mounted at the center. The rinsing, other liquids application, or drying take place as the rotor spins with the carrier and wafers held therein. Stationary retainer bars are typically provided adjacent the open top side of the wafer carrier to prevent the wafers from being displaced if the rotor should stop in an upside-down position. The rotors are also typically controlled to stop in a right-side-up position. This type of spin rinser dryer is normally termed an axial or on-axis spin rinser dryer.
Additionally semiconductor processing machines of similar configuration are also used for centrifugal chemical etching or other chemical processing. In this regard, the required chemicals are pressurized or pumped to the processing chamber and valves control the supply of such chemicals into the chamber. The chemical processing can be following by associated rinsing and drying operations. The application of processing chemicals adds to the complexity of the processing because highly reactive chemicals may impinge upon the wafer surfaces at different angles, fluid velocities, with differing flow rates, and with other dynamically varying effects. This variability can cause different etch rates or other variations in chemical processing which is difficult to overcome.
Process uniformity within a batch and repeatability from batch to batch have been major considerations in semiconductor processing, and in particular centrifugal semiconductor processing. The issue is particularly of interest in the case of batch centrifugal processing because the wafers are held in closely spaced arrays using wafer carriers. In addition to inherent variations in the application of processing fluids to the wafers, there are also variations associated with how wafers are held within the carriers. The structural parts of the carriers necessarily restrict access of fluids to the wafer surfaces. This has almost invariably led to different processing results for wafers in different positions within a carrier, even though processing has occurred in the same batch. Although carriers have been designed to reduce their effects on processing fluid distribution within the processing chamber, it has been impossible to eliminate their effects on uniformity and repeatability of processing results.
While the apparatus and methods utilized heretofore have operated with varying degrees of success, they have also sometimes suffered problems with regard to contamination or particle additions which can occur during processing. As the features and geometries of the discrete components formed on the semiconductor devices have become smaller and more densely packed, the need for more stringent contamination control has become increasingly difficult.
Thus there has been a need in the art of semiconductor wafer and similar article processing for a centrifugal processing machine which provides improved uniformity of process results while minimizing the possibility of contamination. This must be done without substantial risk of damage to the semiconductor wafers.
A further area of significance in the processing of semiconductor articles includes the handling and coordination of wafer carriers commonly used to support semiconductor wafers in various stages of processing and translocation between processes. Wafer carriers are often susceptible to picking up undesirable contaminants. Carriers which have been contaminated can in some processing schemes be used to carry more than one batch of wafers. This increases the potential for spreading contamination amongst multiple wafers and batches.
These and other considerations have led to a novel semiconductor processing system as described herein, with various benefits and advantages which are described or inherent from the construction and description given herein.